Various methods are presently known in the art for the delivery of a pharmaceutical composition to treat various medical conditions. The pharmaceutical composition may be provided to a human or veterinary patient in need of therapeutic treatment by a variety of routes such as, for example, subcutaneous, topical, oral, intraperitoneal, intradermal, intravenous, intranasal, rectal, intramuscular, and within the pleural cavity. Administration of pharmaceutical compositions is usually accomplished orally or parenterally. However, it has become increasingly common to treat a variety of medical conditions by introducing an implantable medical device partly or completely into the esophagus, trachea, colon, biliary tract, urinary tract, vascular system or other location within a human or veterinary patient. For example, many treatments of the vascular system entail the introduction of a device such as a stent, catheter, balloon, guide wire, cannula or the like into the body.
Exposure, however, to a medical device which is implanted or inserted into the body of a patient can cause the body tissue to exhibit adverse physiological reactions. These adverse reactions can occur whether the medical device is introduced by a major surgical procedure or by a minimally invasive technique; they include, for example, the formation of emboli or clots, cell proliferation, occlusion of blood vessels, platelet aggregation, or calcification. To reduce the potential occurrence of such adverse effects associated with implanted medical devices, pharmaceuticals, such as anticoagulants and antiproliferation drugs, have been administered in or on such medical devices.
In addition to administering drugs to treat and/or prevent the adverse reactions to inserted or implanted medical devices, such devices can also be used for the improved localized delivery of drugs to diseased tissues or body lumens in most branches of medicine and for most types of drugs. Such drugs include, for example, antibiotics, anti-inflammatory agents, anti-cancer agents and genetic material for gene therapy. Thus, the medical device enables drugs to be administered locally rather than systemically.
Methods for delivering drugs to body lumens or tissues may involve, for example, the use of catheters having a balloon disposed on the distal end of the catheter, with the drugs coated on the balloon surface. For instance, U.S. Pat. No. 5,102,402 to Dror et al. and U.S. Pat. No. 6,146,358 to Rowe describe medical devices, typically a balloon catheter, in which the exterior surface of the balloon is coated with drugs. Generally, the drugs are applied to the surface of the balloon by known coating methods, including spraying, dipping, rolling, brushing, solvent bonding, adhesives, or welding. The drug is delivered to the target lumen or tissue by inserting the catheter into the body lumen and maneuvering it through the cardiovascular system to the target site. Once in the proper position, the balloon is inflated for contacting the afflicted tissue so that the drug is released and retained in the lumen or tissue as the balloon is deflated.
Rather then being coated directly on the balloon surface, as described supra, the drug may be embedded in a separate polymer layer, which is then coated or otherwise applied to the balloon surface. For instance, U.S. Pat. No. 6,409,716 to Sahatjian et al. and U.S. Pat. No. 6,364,856 to Ding et al. disclose balloon catheters with drug-embedded polymer layers coated upon the balloon surface. These medical devices allow for a rapid release of the drug from the coated polymer layer during compression of the polymer coating against the wall of the lumen as the balloon is expanded. Sahatjian et al. '716 describes a balloon catheter with a swellable hydrogel polymer layer adhered to the surface of the balloon, whereas Ding et al. '856 discloses a balloon catheter with a sponge non-hydrogel polymer coating applied to the surface of the balloon.
Drug-coated medical devices of the foregoing types do, however, have certain disadvantages. For example, the application of a separate coating (either of the drug itself or of a drug-containing layer) to the balloon surface usually involves multiple steps. The coating may not adhere properly to the balloon surface, thereby causing difficulties when using the device. For example, inserting or implanting the medical device may be difficult if the coating is not properly adhered to the balloon surface. In addition, the effectiveness of the drug application may be hampered if the coating has been compromised.
Hence, there is a need for a device which reliably delivers drugs, therapeutic agents, or bioactive materials directly into a localized tissue area so as to treat and/or prevent conditions and diseases.